Tannins are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids.
Polyphenols are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.
The water caltrop is any of three extant species of the genus Trapa: Trapa natans, Trapa bicornis and the endangered Trapa rossica. It is also known as buffalo nut, bat nut, devil pod, ling gok, ling nut, lin kok, ling jow, ling kio nut, mustache nut, singhara or water chestnut.
Ellagic acid is a polyphenol found in numerous fruits and vegetables. It is the dilactone of hexahydroxydiphenic acid.
In organic chemistry, the Arndt–Eistert reaction is the conversion of a carboxylic acid to its homologue. Named for the German chemists Fritz Arndt (1885–1969) and Bernd Eistert (1902–1978), the method entails treating an acid chlorides with diazomethane. It is a popular method of producing β-amino acids from α-amino acids.
The Nierenstein reaction is an organic reaction describing the conversion of an acid chloride into a haloketone with diazomethane. It is an insertion reaction in that the methylene group from the diazomethane is inserted into the carbon-chlorine bond of the acid chloride.
Terminalia chebula, commonly known as black- or chebulic myrobalan, is a species of Terminalia, native to South Asia from India and Nepal east to southwest China (Yunnan), and south to Sri Lanka, Malaysia, and Vietnam.
The enzyme tannase (EC 3.1.1.20) catalyzes the following reaction:
The phenolic content in wine refers to the phenolic compounds—natural phenol and polyphenols—in wine, which include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenoids, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins). This large group of natural phenols can be broadly separated into two categories, flavonoids and non-flavonoids. Flavonoids include the anthocyanins and tannins which contribute to the color and mouthfeel of the wine. The non-flavonoids include the stilbenoids such as resveratrol and phenolic acids such as benzoic, caffeic and cinnamic acids.
Digallic acid is a polyphenolic compound found in Pistacia lentiscus. Digallic acid is also present in the molecule of tannic acid. Digalloyl esters involve either -meta or -para depside bonds.
A hydrolyzable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids.
Casuarictin is an ellagitannin, a type of hydrolysable tannin. It can be found in Casuarina and Stachyurus species.
Condensed tannins are polymers formed by the condensation of flavans. They do not contain sugar residues.
Quercus infectoria or the Aleppo oak is a species of oak well known for producing galls that have been traditionally used for centuries in Asia medicinally while also used in softening leather and in making black dye and ink.
Casuarinin is an ellagitannin. It is found in the pericarp of pomegranates. It is also found in Casuarina and Stachyurus species and in Alnus sieboldiana.
Pedunculagin is an ellagitannin. It is formed from casuarictin via the loss of a gallate group.
Maximilian Nierenstein was a professor of biochemistry at the University of Bristol.
Alnusiin is an ellagitannin found in Alnus sieboldiana.
Alnus sieboldiana is an alder species found on the islands of Honshū, Shikoku, and Suwanose-jima in Japan.
Bicornin is an ellagitannin found in the Myrtales Trapa bicornis and Syzygium aromaticum (clove).
